apo-PhyB covalently binds to the chromophore phycocyanobilin (PCB) to form a light-sensitive holoprotein. PhyB undergoes conformational changes between the Pr and Pfr states catalysed by red and infrared light, reversibly associating with the PIF domain only in the Pfr state. This heterodimerization interaction can be used to translocate a YFP-tagged PIF domain to PhyB tagged by mCherry and localized to the plasma membrane by the C-terminal CAAX motif of Kras.

When asked about the possibility that this could be used in-vivo, Levskaya said

The only real caveat for in-vivo work is delivery of the non-native PCB tetrapyrrole. From the literature and my experience with cell culture I suspect it shouldn’t be hard to just administer it directly to animals to get saturating levels for holoprotein formation. It might even be possible just to feed animals Spirulina (where it comes from). There’s nutrition literature that suggests their livers are capable of freeing PCB and getting it into the blood stream.

Expression of genetic tools that control neural activity (Channelrhodopsins, Halorhodopsins, DREADDs) in functionally defined populations, such as neurons that are active during a particular task or thought, is the next big leap that needs to be made in systems neuroscience. This may be achieved by combining an imaging technique to identify active neurons, such as G-CaMP3, with photo-switchable transcription. The technique presented in the above paper is one promising avenue which may lead to cell-specific photo-switchable transcription. Once robust versions of these tools are in place, scientists will begin to work out the complex and thrilling processes of reverse-engineering and manipulation of specific thoughts and memories, at least in mice and rats.

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23092009

Graham(08:49:29) :

So when one is told “Nature does not publish methods papers” by editors, it turns out to be a complete lie.
The journal does indeed publish methods with substantial biological hypotheses. As long as the editors think the method is sexy.